This program is concerned wth several phases of the general problem ofthe physiology of the renin-angiotensin-aldosterone system and sodium metabolism in hypertension and congestive heart failure. The specific areas include: 1) the role of angiotensin II in renal hypertension andin hemorrhage in the dog, 2) the pathogenesis of spontaneous hypertension in the rat, 3) the control of renin released by the kidney in the dog, 4) the control of the renal circulation in the dog, 5) the control of aldosterone secretion in the rat, and 6) the physiology of thoracic caval constriction in the rabbit. During the present year, we plan to continue to studythe control of reninsecretion in the dog. Presently, we are concentrating on defining better the adrenergic recptors involved. Secondly, as a high priority item we plan to place emphasis on the study of experimental hypertension. We will be doing in depth studies on the pathogenesis of steroid secretion in the spontaneous hypertensive rat. In the dog, with renal hypertension, we will attempt to define the changes in the renalcirculation in sodium- depleted dogs and in dogs with high output heart failure secondary to an A-V fistula. The purpose in defining better the pathogenesis of ascites in rabbits with thoracic caval constriction is to provide another model with increased activity of the renin-angiotensin system for use in studying the pathogenesis of renal hypertension in the rabbit.